Abstract
Although monoclinic WO3 is widely studied as a prototypical photoanode material for solar water splitting, limited success, hitherto, in fabricating WO3 photoanodes that simultaneously demonstrate high efficiency and reproducibility has been realized. The difficulty in controlling both the efficiency and reproducibility is derived from the ever-changing structures/compositions and chemical environments of the precursors, such as peroxytungstic acid and freshly prepared tungstic acid, which render the fabrication processes of the WO3 photoanodes particularly uncontrollable. Herein, a highly reproducible sol-gel process was developed to establish efficient and translucent WO3 photoanodes using a chemically stable ammonium metatungstate precursor. Under standard simulated sunlight of air mass 1.5 G, 100 mW cm−2, the WO3 photoanode delivered photocurrent densities of ca. 2.05 and 2.25 mA cm−2 at 1.23 V versus the reversible hydrogen electrode (RHE), when tested in 1 mol L−1 H2SO4 and CH3SO3H, respectively. Hence, the WO3 photoanodes fabricated herein are one of the WO3 photoanodes with the highest performance ever reported. The reproducibility of the fabrication scheme was evaluated by testing 50 randomly selected WO3 samples in 1 mol L−1 H2SO4, which yielded an average photocurrent density of 1.8 mA cm−2 at 1.23 VRHE with a small standard deviation. Additionally, the effectiveness of the ammonium metatungstate precursor solution was maintained for at least 3 weeks, when compared with the associated upper-limit values of peroxytungstic and tungstic acid based precursors after 3 d. This study presents a key step to the future development of WO3 photoanodes for efficient solar water splitting.
摘要
单斜相WO3是一种用于太阳能水分解反应的经典光阳极材 料, 但如何可靠地制备高效WO3光阳极仍具有挑战性. 这主要是由 于常用的过氧钨酸及新制钨酸前驱体的成分/结构及化学环境不断 变化, 使得后续的制备过程不可控. 本文报道了一种以化学稳定性 好的偏钨酸铵作为前驱体的溶胶-凝胶策略, 可获得高效、高重复 性的WO3光阳极. 结果表明在模拟太阳光辐照下最优WO3光阳极 在可逆氢电极1.23 V处可产生2.05与2.25 mA cm−2(1 mol L−1 H2SO4及CH3SO3H中)的光电流. 随机选择的50片WO3光阳极于 1 mol L−1 H2SO4中的测试结果表明在1.23 V处的光电流平均值为 1.8 (±0.12) mA cm−2. 此外, 偏钨酸铵前驱体溶液可持续生效至少 三周, 而过氧钨酸及新制钨酸前驱体的有效时间不超过三天. 本研 究为构建高效WO3光阳极提供了新的研究思路与实验基础.
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Acknowledgements
This work was supported by the Ministry of Education (MOE) Tier 1 (M4011959 and M4011528), the National Key Research and Development Program of China (2018YFA0209303), the National Natural Science Foundation of China (U1663228 and 51902153) and the Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions.
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Feng J, Zhao X, Li Z and Huang Y designed the research; Feng J, Zhao X, Zhang B, Yang G, Qian Q, and Ma S fabricated the samples, performed the current-potential curve, XRD, ultraviolet-visible spectra, SEM and IPCE measurements; all the authors discussed the results and co-wrote the paper.
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The authors declare that they have no conflict of interest.
Jianyong Feng obtained his PhD at Nanjing University in 2014, then he worked as a postdoctoral fellow at Nanyang Technological University, Singapore. Since 2017, he has been a research scientist at the College of Engineering and Applied Sciences, Nanjing University. His research interests are photoelectrochemical water splitting and solar cells.
Xin Zhao received his BSc from China Agricultural University in 2009, and PhD from Nanjing University in 2014, respectively. He joined the School of Materials Science and Engineering at Nanyang Technological University as a research fellow in 2014, working with Prof. Zhong Chen, and then moved to the School of Physical &;amp; Mathematical Sciences with Dr. Han Sen Soo. His current interests include photoluminescence, photoelectrochemistry for solar energy conversion, earth-abundant elements to valorize biomass lignin and degrade environmental pollutants by ambient condition C-C bond activation.
Zhaosheng Li received his PhD in condensed matter physics from the Institute of Solid State Physics, Chinese Academy of Sciences, China, in 2003. After a two-year postdoctoral fellowship at Nanjing University, he became a lecturer at this university. In 2006, he was promoted to an Associate Professor of materials science and engineering at Nanjing University. Since Dec 2011, he has become a full Professor of materials science and engineering at the College of Engineering and Applied Sciences, Nanjing University. His current research interests are photoelectrochemistry and photocatalysis.
Yizhong Huang is currently positioned in the School of Materials Science and Engineering at Nanyang Technological University in Singapore. He has been working in the University of Oxford as a postdoc and then research fellow (faculty member) and college fellow of Wolfson and now an academic visitor. He has developed his expertise in transmission electron microscopy (TEM) and focused ion beam (FIB) system with specific research interests in nano-electrochemistry and hybrid nanostructured materials for energy applications.
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Feng, J., Zhao, X., Zhang, B. et al. Sol-gel synthesis of highly reproducible WO3 photoanodes for solar water oxidation. Sci. China Mater. 63, 2261–2271 (2020). https://doi.org/10.1007/s40843-020-1430-4
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DOI: https://doi.org/10.1007/s40843-020-1430-4